Contents

Python NumPy For Your Grandma - 4.8 Challenge: Movie Ratings

Setup

You’re given a 10x2 array of floats where each row represents a movie. The first column represents the movie’s rating and the second column represents the director’s rating. Your goal is to create a third column to represent the overall rating. The overall rating is equal to the movie rating if it exists, otherwise it’s the director’s rating.

import numpy as np

generator = np.random.default_rng(123)
ratings = np.round(generator.uniform(low = 0.0, high = 10.0, size = (10, 2)))
ratings[[1,2,7,9], [0,0,0,0]] = np.nan
print(ratings)
## [[ 7.  1.]
##  [nan  2.]
##  [nan  8.]
##  [ 9.  3.]
##  [ 8.  9.]
##  [ 5.  2.]
##  [ 8.  2.]
##  [nan  6.]
##  [ 9.  2.]
##  [nan  5.]]

Solution 1

x = np.where(np.isnan(ratings[:, 0]), ratings[:, 1], ratings[:, 0])
result = np.insert(arr = ratings, values = x, axis = 1, obj = 2)
print(result)
## [[ 7.  1.  7.]
##  [nan  2.  2.]
##  [nan  8.  8.]
##  [ 9.  3.  9.]
##  [ 8.  9.  8.]
##  [ 5.  2.  5.]
##  [ 8.  2.  8.]
##  [nan  6.  6.]
##  [ 9.  2.  9.]
##  [nan  5.  5.]]

Solution 2

x = np.where(np.isnan(ratings[:, 0]), ratings[:, 1], ratings[:, 0])
result = np.hstack((ratings, x[:, None]))
print(result)
## [[ 7.  1.  7.]
##  [nan  2.  2.]
##  [nan  8.  8.]
##  [ 9.  3.  9.]
##  [ 8.  9.  8.]
##  [ 5.  2.  5.]
##  [ 8.  2.  8.]
##  [nan  6.  6.]
##  [ 9.  2.  9.]
##  [nan  5.  5.]]

Course Curriculum

  1. Introduction
    1.1 Introduction
  2. Basic Array Stuff
    2.1 NumPy Array Motivation
    2.2 NumPy Array Basics
    2.3 Creating NumPy Arrays
    2.4 Indexing 1-D Arrays
    2.5 Indexing Multidimensional Arrays
    2.6 Basic Math On Arrays
    2.7 Challenge: High School Reunion
    2.8 Challenge: Gold Miner
    2.9 Challenge: Chic-fil-A
  3. Intermediate Array Stuff
    3.1 Broadcasting
    3.2 newaxis
    3.3 reshape()
    3.4 Boolean Indexing
    3.5 nan
    3.6 infinity
    3.7 random
    3.8 Challenge: Love Distance
    3.9 Challenge: Professor Prick
    3.10 Challenge: Psycho Parent
  4. Common Operations
    4.1 where()
    4.2 Math Functions
    4.3 all() and any()
    4.4 concatenate()
    4.5 Stacking
    4.6 Sorting
    4.7 unique()
    4.8 Challenge: Movie Ratings
    4.9 Challenge: Big Fish
    4.10 Challenge: Taco Truck
  5. Advanced Array Stuff
    5.1 Advanced Array Indexing
    5.2 View vs Copy
    5.3 Challenge: Population Verification
    5.4 Challenge: Prime Locations
    5.5 Challenge: The Game of Doors
    5.6 Challenge: Peanut Butter
  6. Final Boss
    6.1 as_strided()
    6.2 einsum()
    6.3 Challenge: One-Hot-Encoding
    6.4 Challenge: Cumulative Rainfall
    6.5 Challenge: Table Tennis
    6.6 Challenge: Where’s Waldo
    6.7 Challenge: Outer Product